Non-invasive methods for determining glucose concentration in human blood based on measuring the electrical impedance of a human body part or impedance components are known.
For example, a method for the indication of sugar content in human blood is known [RU Pat. No. 2073242, G01N33/4, 1997], with which sugar content level is determined based on variation of dielectric permeability of a finger placed in the electrical field of transducer.
A method for monitoring the amount of sugar in human blood is also known [RU Pat. No. 2088927, G01N33/49, 1997], with which the measurement is taken by changing the reactance of oscillating circuits included in the secondary circuits of high-frequency generator via direct action of human upon oscillating circuits elements. With this method, the amount of sugar in blood is determined based on variation of current in the secondary circuits of high-frequency generator.
Another method is known [U.S. Pat. No. 5,792,668, G01N27/00, 1998], with which spectral analysis of high-frequency radiation reflected by human body or passing through the human body is conducted. The phase shift between direct and reflected (or transmitted) waves, which characterizes the reactive component of electrical impedance, represents a parameter to be measured by this method. The concentration of substances contained in the blood (in particular, glucose concentration) is determined based on measured parameters of phase spectrum.
Another method is known, which was embodied in a device described in the RU Pat. No. 9703U1, A61B5/00, 1999. Glucose concentration is determined by this device based on measurement of human body region impedance at two frequencies, determining capacitive component of impedance and converting the obtained value of capacitive component into glucose concentration in patient's blood.
A method for measuring glucose concentration in human blood non-invasively is known [U.S. Pat. No. 6,517,482, A61B5/00, 2003]. The method is based on measuring impedance between two electrodes at a number of frequencies and deriving the value of glucose concentration on the basis of measured values.
Another method for determining glucose concentration in blood non-invasively is known, which involves measuring electric transfer functions by means of two pairs of four-electrode sensors [RU Pat. No. 2342071, A61B5/053, 2008]. The concentration of glucose in blood is determined based mathematical model specified in advance.
Another method for determining glucose concentration in human blood is also known [U.S. Pat. No. 7,050,847, A61B5/00, 2006], with which impedance of a human body area is measured at different frequencies by means of sensors. Impedance value at high frequencies is related to fluid volume in body tissues, while impedance value at low frequencies—to volume of extracellular fluid. Parameters of biological fluids in the human body are determined based on the measured values, and then glucose concentration in human blood is derived from these parameters.
However, the above-described methods are characterized by one common disadvantage—namely, the values of glucose concentration in human blood obtained through the use of these methods rank below the values obtained using direct invasive methods in terms of measurement accuracy. At the same time, invasive methods, which require taking samples of blood, rank below non-invasive ones in terms of convenience and safety.
An engineering problem to be solved by the present invention consists in working out a non-invasive method for continuous determination of glucose concentration in human blood that is characterized by higher accuracy as compared to currently known non-invasive methods.